2006 OPEN FORUM Abstracts
Comparing Resistance Across The Expiratory LIMB of the Limb-O Circuit vs a Heated-Wire Circuit
Ross
Armstrong RRT1, Nikolas Sirs RRT2, Lonny
Ashworth MEd RRT3. 1St. Luke's Regional Medical Center, Boise, ID 2Northern Colorado Medical Center, Greeley, CO 3Boise State University, Boise, ID
Background: The Limb-O circuit (Vital
Signs, Inc.) is a single-lumen circuit designed to have less tubing at the
bedside, no need for additional humidification and less weight on the patient's
airway. Equipped with a heat moisture exchanger (HME), the Limb-O circuit is
commonly used on patients who require shorter periods of mechanical ventilation
or during noninvasive mechanical ventilation. According to the manufacturer, the
smooth common wall found inside the tubing, reduces turbulent flow resulting in
a resistance that is comparable to a traditional ventilator circuit. The purpose
of this study is to evaluate the resistance across the expiratory limb of the
circuit when using a Limb-O circuit versus a traditional heated-wire circuit.
Methods: A Dräger
XL ventilator, with a CMV rate 12 BPM and tidal volume 500 mL, was used with a
Limb-O circuit and heated-wire circuit. To measure the resistance across the circuit,
pressure and flow transducers were connected at the patient wye and immediately
before the exhalation valve. Each circuit was then connected to a Hans Rudolph
Electronic Breathing Simulator (HR 1101). A compliance of 100, 80, 60, 40 and 20
mL/cm H2O and PEEP of 3, 6, 9, 12 and 15 cm H2O were used.
Results: The expiratory resistance was
higher using the Limb-O circuit than the heated-wire circuit at each compliance
and PEEP setting. At PEEP of 6 cm H2O and decreasing compliance
from 100, 80, 60, 40 and 20 mL/cm H2O, the average resistance using
the Limb-O circuit was 4.73, 4.92, 5.45, 6.27, 8.52 cm H2O/L/sec respectively, and using the heated-wire circuit was 1.77,
2.09, 2.48, 3.03, 4.3 cm H2O/L/sec respectively. This
trend in expiratory resistance was similar at each PEEP setting.
Conclusion: Based on these findings,
there is an increase in resistance across the expiratory limb of the Limb-O
circuit as compared to a heated-wire circuit when ventilating an electronic
lung simulator. Additional studies are needed to determine whether or not this
is clinically significant on patients. This study was performed without
additional heat or humidification; results may vary when using heated,
humidified circuits.